The growing concern for noise pollution has lead to various types of ear protection devices. One type of device which has found great success is a foam earplug. For example, foam earplugs are known which are made of slow recovery material so that the earplugs can initially be of a cross-sectional area larger than the ear canal and then twirled and compressed to a cross-sectional area smaller than the ear canal to facilitate the insertion of the earplug into the ear. After the twirling has ceased the earplug begins to return to its original shape. Because of its slow recovery characteristic, however, sufficient time remains to permit the earplug to be inserted into the ear whereupon the earplug is effectively seated in the ear without reaching its fully relaxed dimensions.
The conventional shape for such slow recovery foam earplugs is of a circular cross-section as from a cylindrical shape. This shape was selected, apparently, because it would offer no corners which might irritate or cause discomfort to the wearer. In the manufacture of such earplugs by punching from a sheet, a great deal of waste material results because of the circular shape of the earplugs.
A variation of the cylindrical earplug is an earplug having a hexagonal cross-section. Here again, a hexagon appears to have the advantage of having its sides meet at such large angles to each other that there is thought to be minimal discomfort to the wearer. Theoretically, hexagonal earplugs could be punched from a sheet with no waste material resulting. In practice, however, it is found that severe compression accompanies the punching operation as it does with circular cross-section earplugs which causes membrane rupture between the foam cells. This reduces air flow resistance and deteriorates the sound attenuating properties of the foam. Still further, when such foam is compressed for punching portions often fail to compress uniformly which results in malformed plugs causing waste and necessitating a close inspection of the product.